I've no idea what your damage looks like. However typically I wouldn't just pump epoxy resin into it and call it ready for prime time. Properly you should sand and feather back from the damaged area and then lay in new cloth and resin. That will better address the tensile, compression and torsion forces that area of the stay is supposed to bear.

If you just fill the entire thing with resin, then it's possible it might fail faster. Or at least make the bumps you hit while riding, bumpier.